A vehicle display light of conventional design is in the form of a block or unit which comprises at least one reflector in which an incandescent or fluorescent lamp is mounted, together with a transparent glass or globe which is mounted in front of the reflector. Such a light is relatively thick, and presents problems of adaptation to the support on which it is mounted, this support being typically a corner region of a vehicle, or a wing of the latter.
In general terms, light bulbs are fragile, have a relatively useful life, and are extravagant of energy. For this reason, proposals have been made in the past to provide signal lights in which the light source comprises a group of semiconductor light emitters, such as electroluminescent diodes. Such arrangements offer the possibility of providing, for example, illuminating diodes in two colours (such as the red and orange customary in warning indications given in automotive applications), while being uncoloured when extinguished. This enables a uniform appearance to be obtained when the light is extinguished.
Such a signal light is described and shown for example in the specification of United Kingdom published patent application No. GB 2 139 340A and the corresponding French published patent application No. FR 2 545 195A. In that document, an arrangement is described in which light emitting diodes are mounted by being secured to a support plate which is so shaped as to receive small wafers electroluminescent diodes in cavities, and which is arranged to carry an electrical circuit for providing the connections between these wafers. The latter are covered with a protective layer. A matrix is thus formed, comprising a plurality of diode wafers with common encapsulation and a common diffusing glass.
This arrangement leads to providing, on the support plate that defines a support element, and on the protective layer, a deposited layer of reflective aluminium. This results in a relatively complicated form of construction which necessitates complex manufacturing techniques under clean conditions, which in turn necessitates costly capital investment. For these reasons, such an arrangement is not open to adoption by a manufacturer of motor vehicle signal lights.
In order to simplify the support element (the plate), an approach may be considered, as disclosed in the specifications of French published patent applications FR 2 481 563A, FR 2 601 486A and FR 2 574 616A and in those of the European published application EP 0 253 244A corresponding to the second of the above mentioned French applications, and U.S. Pat. No. 4,742,432 corresponding to the third of these French applications, in which discrete electroluminescent elements are used. These elements include a support member which carries supply terminals and which has a semiconductor light source or emitter.
In such an arrangement the support element no longer needs to be formed with reflective cavities. It does however pose a new assembly problem. This is that, if an optical collimating element is associated with the support element, in the manner disclosed in the above mentioned United States patent, the optical collimating element has to be finally fitted on to the support element which carries the electroluminescent elements, the latter having previously been fixed on to the support element so as to facilitate fitting of the electroluminescent elements. The optical collimating element is mounted on the electroluminescent elements with a clearance, and is formed with parabolic cavities, with insulating apertures engaging conductive rings of the electroluminescent elements with a small clearance. In some case therefore, the electroluminescent elements cannot be arranged on the optical axis of the parabola, and this is detrimental to performance of the signal light.
In addition, when the light has an irregular or complex shape, for example when it is of bulged or convex form, fitting can become very difficult.
Again, it is generally undesirable to lose the electroluminescent elements, yet the latter are difficult to manipulate and transport with the support element before the electroluminescent elements have been assembled to their electrical circuit, without serious risk of their becoming separated and lost.